Export change id processor.

- Don't declare the plugin directly, it is exported via java_library that defines the sources.
- Remove unneeded framework-annotation-proc.

Bug: 152220864
Test: m && diff merged_compat_config.xml
Change-Id: Ie750b5391229d21679a8610780b9f8d4a997e204
(cherry picked from commit af1a2c4598de7e60b454926e7445caf49e490c76)